Mediastinum - Thymic carcinoma

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Mediastinum

Thymic carcinoma - general

Reviewer: Hanni Gulwani, M.D. (see Reviewers page)
Revised: 27 February 2013, last major update December 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● By definition, has overt cellular anaplasia

Epidemiology
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● Ages 50+, occasionally children

Clinical features
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● Associated with hypercalcemia, elevated parathyroid hormone levels, pulmonary sarcoidosis
● Not associated with paraneoplastic syndromes such as myasthenia gravis or pure red cell aplasia
● Patients usually present with mass related symptoms
● Aggressive clinical course
● Must exclude other primaries, which are much more common (lung, trachea, bronchi, esophagus)
● Usually squamous cell carcinoma and variants (lymphoepithelioma-like, basaloid)
● Proposed staging system (Am J Clin Pathol 2012;138:115)

Prognostic factors
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● May be less aggressive than commonly believed; important prognostic factors are lymph node status and tumor size (Am J Clin Pathol 2012;138:103)

Diagrams
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Proposed stage T1, tumor limited to thymic gland

Proposed stage T2, tumor invades nearby structures

Proposed stage T3, direct (continuous) extrathoracic tumor extension beyond thoracic inlet or below diaphragm

Gross description
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● Unencapsulated, no internal fibrous septation, firm / hard / gritty with gray-white cut surface, necrosis and hemorrhage

Micro description
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● Usually cohesive cellular growth, regularly round/oval nuclear outlines, eosinophilic nucleoli, geographic necrosis
● Usually foci of medullary differentiation, abortive Hassall’s corpuscles, rosettes, gland-like spaces, T lymphocytes; no perivascular spaces,
● Subtypes discussed as separate topics

Micro images
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Histological features (b & d)

CK18, GLUT1, CA-IX, c-kit, CD5, MUC1, CEA

Various subtypes

Positive stains
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● Keratin, CD5, CD70, often EMA, variable CEA (if overt glandular differentiation), c-kit, GLUT1 (Am J Surg Pathol 2000;24:742, Am J Surg Pathol 2011;35:1296, Virchows Arch 2011;458:615)

Negative stains
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● Vimentin, proteasome beta subunit (Am J Surg Pathol 2011;35:1296)

Electron microscopy description
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● Well-formed desmosome-like intercellular junctions, cytoplasmic tonofilaments that may insert into junctional complexes

Differential diagnosis
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● Metastatic carcinoma
● Thymoma type B3: GLUT1 usually negative (Mod Pathol 2009;22:1341)

End of Mediastinum > Thymic carcinoma - general

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